Gas exchange valves of internal combustion engines may be actuated by cams of a camshaft. The opening and closing times of the gas exchange valves may be purposefully defined with the aid of the configuration and shape of the cams. The camshaft is usually actuated, driven and/or activated by the crankshaft of the internal combustion engine. The opening and closing points in time of the gas exchange valves of the internal combustion engine are usually predefined by a relative rotational position/phase angle/angular position between the camshaft and the crankshaft. A variable adjustment of the opening and closing points in time of the gas exchange valves may be achieved by a relative change in this rotational position between the camshaft and the crankshaft. Due to the variable adjustment of the opening and closing points in time of the gas exchange valves, for example the exhaust gas behavior may be positively influenced, the fuel consumption may be decreased, the efficiency may be increased, the maximum torque of the internal combustion engine may be increased and/or the maximum power of the internal combustion engine may be increased, as a function of the instantaneous operating state of the internal combustions engine.
It is customary to use two camshafts in an internal combustion engine, namely one camshaft for controlling the opening and closing points in time of inlet gas exchange valves and the other camshaft for controlling the opening and closing points in time of the outlet gas exchange valves.
The camshafts are usually situated coaxially to each other. In the present case, as a special case of the coaxial arrangement, the camshafts are to be situated or present at least partially or at least in sections, concentrically.
An (outer) part of the camshaft adjuster, referred to here as the stator, is connected to the outer camshaft. At the same time, another (inner) part of the camshaft adjuster, referred to here as the rotor, is connected to the inner camshaft. The variable adjustment of the opening and closing points in time of the gas exchange valves is achieved by a variably adjustable angle between the rotor and the stator. For example, this adjustment may be carried out hydraulically, for example via a fluid, or electrically. The present invention is to be combinable with all camshaft adjusting mechanisms.
To facilitate an undisturbed operation of the camshaft adjuster, the rotor and the stator may preferably be and remain situated concentrically. However, an offset, in particular an angle offset or an axial offset between the camshafts, may occur in concentrically arranged camshafts, for example due to manufacturing tolerances. If the stator were now to be fixedly connected to one camshaft, and if the rotor were to be simultaneously fixedly connected to the other camshaft, the necessary concentricity of the rotor and the stator could no longer be ensured. It is therefore advantageous to improve camshaft adjusters to the effect that they may compensate for or tolerate an offset, in particular an angle offset, between the concentrically arranged camshafts.
For example, the following approach is known from the related art for this purpose. DE 10 2012 105 284 A1 describes a camshaft device, which includes an inner camshaft, an outer camshaft situated concentrically thereto, a camshaft adjuster for adjusting the inner camshaft and/or the other camshaft and a compensating element situated between the inner camshaft and/or the outer camshaft, on the one hand, and the camshaft adjuster, on the other hand, the compensating element having a disk-like shape. This disk-like compensating element forms, for example, a calotte shape and is to be able to compensate for an angle offset between the camshafts. The rotor is axially connected to the inner camshaft with the aid of a central screw, a connecting piece being inserted therebetween, for example via hydraulic channels for the purpose of controlling the camshaft adjuster. Contact surfaces between the screw and the connecting piece and between the connecting piece and the rotor are plane-parallel, i.e., they extend in a radial plane of the axis of the screw, i.e., in a radial plane to the center axis of an axial end section of the inner camshaft. In particular, since or if an axial force is applied by a pretightening of the screw, it is to be assumed that the rotor is oriented toward a screw head contact surface, whereby the function of the compensating element may not be effective. It is therefore to be assumed that the disk-like compensating element is able to compensate for an angle offset only to a limited extent, due to this plane-parallelism. If the angle offset or angle error exceeds the compensatable amount, an inclination occurs, for example between the rotor and the stator, which may result, for example, in a reduced tightness, an increased friction, an increased wear and/or a jamming between the stator and the rotor.